In belt drives with drive wheels that alternately receive and output torque and a corresponding change from tensioned belt section to slack belt section, the tensioning of the slack belt section requires a tensioning device with two tensioning rollers that bias the belt in front of and behind the drive wheel that alternately drives and is driven. This typically—but not necessarily—involves the belt drive of an internal combustion engine with an electric machine in the form of a starter generator that is driven not for the purpose of generating power from the internal combustion engine, but instead also drives the internal combustion engine, in order to start the engine.
Known tensioning devices, as proposed, for example, in DE 199 26 615 A1, DE 10 2008 025 552 A1, and DE 10 2006 019 877 A1, each have a tensioner housing mounted on the starter generator and two tensioning arms that can move in this housing, wherein a force is applied on each other with the corresponding tensioning rollers by a spring component arranged in-between, in order to tension the belt.
A tensioning device of the type named above, i.e., with only one tensioning arm supported so that it can move in the tensioner housing on one side and a housing-fixed tensioning roller on the other side is known from the unpublished documents DE 10 2011 082 764 A1, DE 10 2011 082 330 A1, and DE 10 2011 084 680 A1. The two sliding bearing points for the tensioning arm are formed there as bearing shells that are arranged at a distance to each other either fixed in place in the tensioner housing or fixed in place on the tensioning arm, so that the relative motion in the sliding bearing is realized either between the bearing shell and the tensioning arm or between the bearing shell and the tensioner housing. The distance of the two bearing shells determining the guide length of the tensioning arm and consequently the length of the tensioning arm section in the tensioner housing is determined, on one hand, according to the permissible tilting of the tensioning arm caused by the sliding bearing play perpendicular to the plane of the belt and, on the other hand, for the specified available installation space of the tensioner housing, according to the required installation space of the spring component applying a force on the tensioning arm.